Spark plug and method of making the same



March 16, 1943. J. 5. COLDWELL SPARK. PLUG AND METHOD OF MAKING THE SAME Filed April 1, 1940 2 Sheets-Sheet 1 .Marcb 16, 1943. .1. s. COLDWELL 2,314,128

SPARK PLUG AND METHOD OF MAKING THE SAME Filed April 1, 1940 2 Sheets-Sheet 2V INVEQTOR Jul-m 5. E UZdI-JEZZ v BY 4. umwk" ATTORNEY. I

Patented Mar. 16, 1943 John S. Coldwell, Milwaukee, Wis., assignor to Globe-Union Inc., Milwaukee, Via, a corporation of Delaware Application April 1, 1940, Serial No. 327,148

13 Claims. (01. 123-169) faces.

Another object of the invention is to provide a method of producing a spark plug with a fiatto-flat gap, which is simple and practical, ca-

pable of being practiced on a high speed pro-' duction line, and which constitutes the gap of two opposed, preferably parallel, flat surfaces without impairing the strength of either'the center or ground electrode or the capability of either to function with maximum effectiveness. These advantages obtain in a spark plug with a single, fiat-to-fiat gap as well as in spark plugs with a double-or multiple fiat-to-iiat gaps.

Other objects and advantages reside in certain novel features of construction, arrangement, and combination of'parts, which will be hereinafter more fully described and particularly pointed out in the appended claims, reference being had to the accompanying drawings forming a part of this specification, and in which:

Figure 1 is a view in bottom plan showing a spark plug constructed in accordance with the present invention.

Figure 2 is a view thereof partly in side elevation and partly in transverse, vertical cross section, the plug being shown inverted.

Figure 3 is a view in side elevation of the lower end of the spark plug.

Figures 4 and 5 are detailed elevational views showing one of the ground electrodes employed in this embodiment of the invention.

Figure dis a view in bottom plan of the spark plug having a single, fiat-to-fiat gap embodying the present invention.

Figure '7 is a view in bottom plan of a spark plug embodying the present invention and having a center electrode of square formation and four cooperative ground electrodes.

Figure 8 is a fragmentary view in cross section, taken on line 8-8 of Figure 7.

Figure 9 is a view in bottom plan of a spark plug embodying the present invention, having a center electrode of triangular formation an three cooperative ground electrodes.

Figure 10 is a view in bottom plan of a spark plug embodying the present invention and havter electrode.

ing its center electrode of quarter round formation and two cooperative ground electrodes.

Figure 11 is a view in bottom plan of a spark plug embodying the present invention and having the ground electrodes in non-parallel relationship but having the spark gaps defined by flat, opposed or parallel surfaces on the elec trodes.

Figure 12 is a view in bottom plan of a spark plug embodying the present invention, but of the type wherein the ground electrodes are constituted of a sheet metal stamping rather than of stripes or wires.

Figure 13 is a fragmentary view in cross section taken on line l8-l3 of Figure 12.

Figure 14 is a view in bottom plan of the spark plug of the type illustrated in Figures 12 and 13, but showing a different geometrical relationship of the electrodes.

Figure 15 is a fragmentary view in cross section illustrating the spark plug of the type shown in Figures 1 to 5 as it is completely assembled and before its electrodes are fashioned in accordance with the method of the present invention,

Referring to the drawings, and more particularly'to Figures 1 to 4 thereof, the numeral I0 designates the metallic shell or body of the plug, which has its lower end externally threaded, as at H, so as to be adapted to be screwed in the usual way into the head block of the motor. The insulating body I2 of porcelain or the like is combined with the shell ID in the usual way. In one type of construction the porcelain body is held in place and in compressing relation to its gaskets, one of which is-illustrated at l3, by means of a sleeve or bushing M.

Extending axially through the porcelain body of the insulator is the center electrode I5 of the plug. Ground or side electrodes l6 and H are provided and are cooperably related to the cen- In carrying out the present invention the spark plug is first completely assembled in the manner illustrated in Figure 15. More specifically, the center electrode is combined in the usual way with the insulating or porcelain body so that its inner end projects beyond the tip thereof and the center electrode and insulator are in position in the metal shell and are operatively combined therewith by means of-the gaskets and packing nut, or other means employed for this purpose. The center electrode has its inner end of the usual round formation at this stage of production of the spark plug, and this is necessary to practically facilitate the assembly of the center electrode with the insulating body. And the ground electrodes, which have had their inner ends welded or staked to the inner end of the shell, are still straight and extend from the inner end of the shell parallel to the axis of the spark plug and shell.

When the spark plug has been assembled in this fashion, the ground electrodes have formed thereon in one way or another flats or flat surfaces which lie in predetermined planes with respect to the center electrode. For example, the ground or side electrodes may be constituted of wire of D-shape in cross section, or the flats thereon may be formed by a swaging, pressing or coining operation. These flat surfaces are utilized to correctly position the center electrode in a punch or flattening die, in that they are engaged with fixed gauges in such a punch or die and locate the center electrode in proper relationship to the male and female members of the punch or die. The next operation is flattening of the center electrode by the punch or die. The operation is in the nature of a coining or pressing one which does not abraid or cut away any of the metal of the center electrode but simply enlarges it laterally, and of equal importance forms two flat or plane surfaces thereon which are located in planes parallel to the flats or flat surfaces of the ground electrodes.

The spark plug is next removed from the punch or flattening die, and is then operated upon by a bending tool of the usual character but equipped with a traveling gauge. In this next operation, the flats of the center electrode are successively utilized to control the bending operation of the ground electrodes. First one and then the other of the flats of the center electrode are engaged with or pressed against the traveling gauge, while one of the ground electrodes is inserted in the socket of the bending tool, and while the spark plug is twisted by the operator to bend the ground electrode into operative relationship with the center electrode. During the entire bending operation, and on the completion thereof, the engagement of a flat of the center electrode with the traveling gauge of the bending tool maintains the flat on the ground electrode and the cooperative flat of the center electrode in their respective parallel planes.

The method just described is particularly adapted to the production of spark plugs of the the resulting plug resides in the particular formation of the spark gap. It is defined by 'two opposed or parallel side faces of the center and ground electrodes. Such a construction does not require the use of ground electrodes which will warp, and consequently uncontrollably change the dimensions of the gap, nor does it require the cutting away of the necessary material in the center electrode, and with all it lends itself, when desired, to a multiple gap formation.

Some of the advantages mentioned, however, may be realized in a single gap formation. For example, as illustrated in Figure 6, the spark plug designated generally at 25 may have its center electrode 26 flattened in the manner described, and may have a single ground electrode 21 formed with a flat surface 28 presented to one of the flats of the center electrode in the manneed not be limited to merely flattening two sides of the center electrode. As shown in Figure 7, the spark plug 30 may have its center electrode 3| flattened on four sides. In this construction the ground electrodes, designated at 32, and four in number, may have square or flat end surfaces presented in close, confronting relation to the sides of the square center electrode.

As illustrated in Figure 9, a spark plug, designated at 35, may have its center electrode I pressed or coined to triangular form. In such a construction there are three ground electrodes 31 which have their ends squared and presented in close, confronting relationship to the sides of the triangularly shaped center electrode.

Figure 10 illustrates a spark plug 40 having a center electrode 4| of a quarter round formation with two ground electrodes 42 presented to the fiat faces of the center electrode.

As shown in Figure 11, it is not essential that the ground electrodes be in parallel relationship. In this figure the spark plug, designated generally at 45, has a center electrode 45 with flattened side faces 41 angularly related to each other. Ground electrodes 48 are cooperatively related to the flattened faces of the center electrode, but necessarily these ground electrodes are in non-paralled relationship. In all of the instances, however, it is essential that the surfaces or flats which define each gap of the plug be themselves opposed or parallel.

As illustrated in Figures 12 to 14, inclusive, it is not essential that the ground electrodes be constituted of wire or strip stock. Thus, as shown in Figure 12, the ground electrodes may be formed of a sheet metal stamping, designated generally at 50, which is blanked or stamped out to provide four ground electrodes 5|, each of which has a square-ended face presented in close, confronting parallel relationship to a coined or pressed four-sided tip 52 of the center electrode.

Figure 14 illustrates a variation of the construction shown in Figure 12, in that-the center electrode, designated at 55, is of triangular formation, and that the sheet metal stamping 55 on which the ground electrodes are formed is cut out to provide only the necessary three ground electrodes. In these constructions, however, as in the others. the spark gap is defined by closely confronting, opposed or parallel, flat surfaces of substantial area.

When the spark plug is in operation in an internal combustion engine, the spark gaps function alternately or successively. In this connection it will be appreciated that practically speaking the gaps are never of exactly the same dimensions. Consequently, the electric current will, of course, follow the path of least resistance, and initially will jump the gap of minimum dimensions. As this initially functioning gap continues in use, the metal of the electrodes which constitute it will under the influence of ionization gradually wear away, thereby increasing the dimensions of such gap until it equals or exceeds that of the other gap or gaps, whereupon the gap of the then minimum dimensions will automatically begin to function until a reversal of conditions obtains.

While I have shown and described several constructions in which the invention may be advantageously embodied, it is to be understood that the constructions shown have been selected merely for the purpose of illustration or example,

and that various changes in the size, shape, and, arrangement of parts may be made without departing from the spirit of the invention or the scope of the subjoined claims.

I claim:

1. A spark plug of thecharacter described comprising a metallic shell, an insulating body, means for holding the shell and body assembled and effecting a hermetic seal between these parts, and cooperating electrodes -.carried by the body and shell and having flat, parallel, closely confronting side faces defining a plurality of spark gaps.

2. A spark plug of the character described comprising a metallic shell, an insulating body, means for holding the shell and body assembled and having a hermetic seal between these parts, a center electrode carried by the insulating body, and ground electrodes welded to the shell, said center and ground electrodes having flat, parallel, side faces of substantial area in closely confronting relation to define a plurality of spark gaps.-

3. A spark plug of the character described comprising a metallic shell, an insulating body, means for holding the shell and insulating body assembled and. for effecting a hermetic seal between these parts, a center electrode extending through the body and having its inner end projecting inwardly thereof and formed with fiat side surfaces of substantial area, and a plurality of ground electrodes carried by the inner end of the shell, each of said ground electrodes comprising an angularly bent strip of metal having the end of one section welded to the shell and having its other section extending transversely with respect to the shell and formed with a fiat side face of substantial area having a portion disposed in close confronting relation and parallel to a flat side surface of the center electrode.

4. A spark plug of the character described comprising a metallic shell, an insulating body, means for holding the shell and body assembled and effecting a hermetic seal between these parts, a center electrode extending through the body and having its inner end projecting inwardly thereof and formed with flat, parallel side surfaces of substantial area, and a pair of ground electrodes, each ground electrode comprising an angularly bent metal strip, a weld between one end of each strip and the inner end of the shell, said strips being formed with one section thereof extending substantially parallel to the axis of the shell and the other section thereof extending transversely with respect thereto and provided with a flat side face of substantial area disposed in close confronting relation and parallel to a flat side surface of the center electrode.

5. A spark plug of the character described comprising a metallic shell, an insulating body, means for holding the shell and body assembled and effecting a hermetic seal between these parts, a center electrode having its inner end projecting inwardly of the insulating body and formed with flat side faces of substantial area, and a pair of rfiimd electrodes carried by the inner end of the shell and having flat side faces of substantial area an angularly bent metal strip of D-shape in cross section, and a weld between one end of the strip and the shell, the flat face of the strip and the flat face of the center electrode being disposed in closely confronting parallel relation.

'7. The herein described method of producing a spark plug with a flat-to-flat gap which consists in completely assembling the plug, with its center electrode projecting beyond the tip of the insulator, and with its ground electrode projecting axially from the inner end of the shell and formed with a flat lying in a predetermined plane, utilizing the flat of the ground electrode to correctly position the center electrode, flattening the center electrode to form a flat thereon which lies in a plane parallel to the plane of the flat of the ground electrode, then utilizing the flat of the center electrode to maintain the flats of the center and ground electrodes in their'respec-- tive parallel planes and bending the ground electrode into operative relationship with the center electrode while the flats of both electrodes are maintained in their respective parallel planes.

8. The herein described method of producing a spark plug with double, flat-to-flat gaps, which consists in completely assembling the plug, with its center electrode projecting beyond the tip of the insulator, and with its ground electrodes projecting axially from the inner end of the shell and formed with flats lying in predetermined planes, utilizing the flats of the ground electrodes to correctly position the center electrode, flattening the center electrode while so positioned to form two flats on the center electrode which lie in planes parallel to the planes of the flats of the ground electrodes, and then successively utilizing the flats of the center electrode to maintain the flats of the center and ground electrodes in respective parallel planes and bending each ground electrode into operative relationship with the center electrode so that during and after the bending of each ground electrode the flats of the ground and center electrodes will be retained in their respective parallel planes.

'9. The method of constructing a spark plug having a central electrode and a shell electrode which comprises forming longitudinally extendin close confronting relation and parallel to the ing flats on the sides of the two electrodes along spaced chords of the shell and bending the shell electrode into position in which it extends across the shell along a chord spaced from a diameter of the shell and the flat thereon is spaced from the flat on the center electrode in substantial parallelism therewith.

11. The method of constructing a spark plug having a central electrode and a shell electrode which comprises forming a longitudinally extending flat on the side of the shell electrode while it extends longitudinally from the shell, locking the central electrode in assembly with the shell, forming a longitudinally extending flat on the side of the central electrode in substantial parallelism with the flat on the shell electrode, and bending the shell electrode into position in which it extends across the shell along a chord spaced from and substantially parallel to a dimeter of the shell and the flat thereon is spaced from the flat on the central electrode.

12. The method ofv constructing a spark plug having a central electrode and a shell electrode which comprises forming a flat on the side of the shell electrode while it extends longitudinally from the shell, said flat being on a chord of the shell, locking the central electrode in assembly with the shell, forming a flat on the side of the central electrode in substantial parallelism with the flat on the shell electrode and on another chord of the shell, and bending the shell electrode into position in which it extends across the shell along a chord spaced from and substantially parallel to a diameter of the shell and the v flat thereon is spaced from the flat on the dentrai electrode.

13. The method of constructing a spark plug which comprises securing a central electrode in a shell in insulated relation thereto, said shell having a shell electrode extending longitudinally therefrom, forming flats on the sides of the central electrode and.the shell electrode with such flats in substantial parallelism, and bending the shell electrode into a position in which it extends across the shell along a chord spaced from and substantially parallel to a diameter of the shell and the flat thereon isadjacent to but spaced from the flat on the central electrode.

JOHN S. COLDWELL. 

